Here are just a few examples of common mistakes made by students of English
as a foreign language in the UK:

One and a half

- Wrong: "I've been in Scotland for one and a half month" (or "one
month half")
- Right: "I've been in Scotland for one and a half months"
One and a half is more than one, so the noun ("month") must be plural
("months"). It is better not to split numbers: "one and a half
months", not "one month and a half".

The UK

- Wrong: "I like UK very much"
- Right: "I like the UK very much"
"UK" is short for "United Kingdom"; "kingdom"
is a noun, so it needs an article (eg: "a" or "the") - there
is only one United Kingdom, so it must be "the United Kingdom".

Almost all

- Wrong: "Almost of the people in my class are Japanese"
- Right: "Almost all of the people in my class are Japanese"
or "Nearly all of the people in my class are Japanese" or "Almost
everybody in my class is Japanese"
The sentence "Most of the people in my class are Japanese" is correct.
But when you want to stress that there are very few people from other countries
in your class, you must say "Almost all of the people in my class are Japanese".

English

- Wrong: Saying that someone from Wales, Scotland or Ireland is "English"
- Right: You can call someone from Wales "Welsh" or "British".
You can call someone from Scotland "Scottish" or "British".
You can call someone from Ireland "Irish" (or "Northern Irish"
if the person is from Northern Ireland)
You need to know something about the history of the United Kingdom to understand
why this mistake annoys people. For details, see: Britain/Countries.

Scary

You are frightened about something.
- Wrong: "I'm scary"
- Right: "I'm scared"
If you say "I'm scary" it means that you make other people afraid
of you (like a monster or a ghost).

Agreeing with negative statements

Your friend says: "I don't like my teacher"
- Wrong reply: "Me too"
- Right reply: "Me neither" (or "I don't like mine either")
If a person makes a negative statement - where the main verb is made negative
using "not" - and you agree with what has been said, you should say
"Me neither".

Your friend says: "I dislike my teacher"
- Wrong reply: "Me neither"
- Right reply: "Me too" (or "I dislike mine too")
Even though the statement in this second example expresses the same idea as
in the first example, the main verb has not been made negative using "not".

Answering negative questions

You don't like your teacher. Your friend asks you: "Don't you like your
teacher?"
- Wrong reply: "Yes"
- Right reply: "No" or "No, I don't"
If someone asks you a question in which the main verb has been made negative
using "not", you should answer "no" if you agree with the
statement form of the question (in this case the statement form of the question
is "You do not like your teacher"). To avoid any possible misunderstanding,
it is better to repeat the negative verb or to answer using a full sentence
("No, I don't" or "No, I don't like my teacher")

You don't like your teacher. Your friend asks you: "You don't like your
teacher, do you?"
- Wrong reply: "Yes"
- Right reply: "No" or "No, I don't"
The main verb is still "do not like". The "do you?" at the
end is just a way of turning the statement "You don't like your teacher"
into a question.

You like your teacher. Your friend asks you: "Don't you like your teacher?"
- Wrong reply: "No", or just "Yes"
- Right reply: "Yes - I like her"
The person asking a negative question is expecting you to agree by saying "no",
so if you want to disagree (because you like your teacher) you need to stress
your answer. In this case it is done by stressing the word "yes",
and to make your meaning clear you should say a full sentence.

You like your teacher. Your friend asks you: "You don't like your teacher,
do you?"
- Wrong reply: "No", or just "Yes"
- Right reply: "Oh yes I do"
"Oh yes I do" is a way of disagreeing with a question that ends "do
you?" (similarly, if someone says, "You aren't hungry, are you?"
and you feel hungry, you can answer "Oh yes I am").

One word or two?

Some words are made by combining two short words which each have only one sound
(monosyllables). It is a common mistake to write these using two words instead
of as one.
- Wrong: bed room, bath room, good night, on line
- Right: bedroom, bathroom, goodnight, online

Very

You cannot use "very" together with an adjective which already has
the idea of being "very" something. Examples of these kinds of adjectives
are: "delicious" means "very tasty", enormous means "very
big", "lovely" means "very nice", "great"
means "very good".
- Wrong: "British food is very delicious"
- Right: "British food is delicious"

Next

Explaining dates in the future, for example when arranging to meet someone,
can be confusing. For example, if today is Monday and you say you will meet
someone "next Friday" what does it mean? It would be clearer to say
"this Friday" or "Friday this week" for the nearer date,
or "Friday next week" or "the Friday after next" for the
later date. British people find it confusing too - so don't worry about asking
them to make it clear what they mean. Another common mistake is:
- Wrong: "I'll see you next next week"
- Right: "I'll see you the week after next"